Answer: The reason is that the cat is marking the objects in his own territory which enable him later to identify it and feel reassured at the familiarity of his surroundings.
There are scent glands on either said of the forehead between the eye and ear (temporal glands) and around the lips, particularly at the corners (perioarl glands). These produce secretion which the cat smears on such things as doorways, stair posts and the legs of furniture as it rubs its cheeks against them. There are also scent glands and the tail ( caudal glands) which deposit similar secretions as the cat brusher its erect moving tail against a favorite object. Glands are also be found around the anus and probably on the pads of the feet.
People who are favorably regarded by the cat are also similarly marked as it rubs against them with its cheeks and tail, often purring vigorously at the same time. This rubbing is the type of affectionate behavior which a kitten shows towards its mother, but also it serve to identify that person as belonging to the special territory of the cat.
